U.S. patent number 11,251,667 [Application Number 16/544,329] was granted by the patent office on 2022-02-15 for permanent magnet modules for an electric machine having axially and circumferentially offset permanent magnet elements, a rotor, permanent magnet electric machine, and a method for assembling thereof.
This patent grant is currently assigned to THE SWITCH DRIVE SYSTEMS OY. The grantee listed for this patent is The Switch Drive Systems Oy. Invention is credited to Panu Kurronen, Tuomas Akseli Pihlaja.
United States Patent |
11,251,667 |
Kurronen , et al. |
February 15, 2022 |
Permanent magnet modules for an electric machine having axially and
circumferentially offset permanent magnet elements, a rotor,
permanent magnet electric machine, and a method for assembling
thereof
Abstract
Each permanent magnet module for a permanent magnet rotor
includes a base-plate and a permanent magnet element attached to
the base-plate. The base-plate includes a bottom section and an
upper section between the bottom section and the permanent magnet
element. The permanent magnet modules constitute subsets so that
permanent magnet modules of different subsets differ from each
other by positions of the upper sections of the base-plates with
respect to the bottom sections of the base-plates so that the
permanent magnet elements of the permanent magnet modules of the
different subsets are axially successive and circumferentially
shifted when the bottom sections of these permanent magnet modules
are axially successive and circumferentially aligned. Thus, the
permanent magnet elements of the permanent magnet modules can be
arranged into, for example, skewed rows on a surface of the
rotor.
Inventors: |
Kurronen; Panu (Lappeenranta,
FI), Pihlaja; Tuomas Akseli (Virolahti,
FI) |
Applicant: |
Name |
City |
State |
Country |
Type |
The Switch Drive Systems Oy |
Lappeenranta |
N/A |
FI |
|
|
Assignee: |
THE SWITCH DRIVE SYSTEMS OY
(Lappeenranta, FI)
|
Family
ID: |
67620302 |
Appl.
No.: |
16/544,329 |
Filed: |
August 19, 2019 |
Prior Publication Data
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Document
Identifier |
Publication Date |
|
US 20200083765 A1 |
Mar 12, 2020 |
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Foreign Application Priority Data
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Sep 12, 2018 [FI] |
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20185758 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02K
1/27 (20130101); H02K 1/274 (20130101); H02K
1/28 (20130101); Y02E 10/72 (20130101); H02K
1/278 (20130101); H02K 7/1838 (20130101); H02K
15/03 (20130101) |
Current International
Class: |
H02K
1/28 (20060101); H02K 1/27 (20220101); H02K
15/03 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2348612 |
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Jul 2011 |
|
EP |
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2523316 |
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Nov 2012 |
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EP |
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2555393 |
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Feb 2013 |
|
EP |
|
2 830 192 |
|
Jan 2015 |
|
EP |
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WO 2010/070196 |
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Jun 2010 |
|
WO |
|
Other References
Finnish Search Report issued in Application No. 20185758, dated
Apr. 3, 2019. cited by applicant .
European Search Report, dated Jan. 10, 2020, for European
Apptication No. 19191425.8. cited by applicant.
|
Primary Examiner: Zhang; Jue
Assistant Examiner: Singh; David A.
Attorney, Agent or Firm: Birch, Stewart, Kolasch &
Birch, LLP
Claims
What is claimed is:
1. Permanent magnet modules for a rotor of a permanent magnet
electric machine, each of the permanent magnet modules comprising:
a base-plate; and a permanent magnet element attached to the
base-plate, wherein the base-plate comprises a bottom section and
an upper section between the bottom section and the permanent
magnet element, wherein the permanent magnet modules constitute at
least three subsets of the permanent magnet modules so that the
permanent magnet modules of different ones of the subsets differ
from each other by positions of the upper sections of the
base-plates with respect to the bottom sections of the base-plates
so that the permanent magnet elements of the permanent magnet
modules of the different ones of the subsets are axially successive
and circumferentially at different positions when the bottom
sections of these permanent magnet modules are axially successive
and circumferentially aligned with each other on a surface of a
body part of the rotor.
2. The permanent magnet modules according to claim 1, wherein the
bottom sections of the permanent magnet modules are shaped to
enable the permanent magnet modules to be shape-locked in radial
and circumferential directions to axially directed fastening rails
located on the surface of the body part of the rotor and to enable
the permanent magnet modules to be slid in an axial direction along
the axially directed fastening rails.
3. The permanent magnet modules according to claim 2, wherein the
bottom section of each of the permanent magnet modules comprises
fastening edges for shape-locking the permanent magnet module under
consideration in the radial and circumferential directions to
between adjacent ones of the axially directed fastening rails.
4. The permanent magnet modules according to claim 3, wherein each
of the fastening edges comprises a flange section enabling the
axially directed fastening rails to press the permanent magnet
module under consideration against the body part of the rotor.
5. A rotor for a permanent magnet electric machine, the rotor
comprising: a body part having a shaft, and permanent magnet
modules on a surface of the body part, wherein each of the
permanent magnet modules comprises a base-plate and a permanent
magnet element attached to the base-plate, the base-plate comprises
a bottom section and an upper section between the bottom section
and the permanent magnet element, and the permanent magnet modules
constitute at least three subsets of the permanent magnet modules
so that the permanent magnet modules of different ones of the
subsets differ from each other by positions of the upper sections
of the base-plates with respect to the bottom sections of the
base-plates so that the permanent magnet elements of the permanent
magnet modules of the different ones of the subsets are axially
successive and circumferentially at different positions when the
bottom sections of these permanent magnet modules are axially
successive and circumferentially aligned with each other on the
surface of the body part, and wherein the permanent magnet elements
of the permanent magnet modules are arranged into rows extending in
an axial direction of the rotor and deviating from the axial
direction of the rotor, and the bottom sections of the permanent
magnet modules are arranged into axially directed straight
rows.
6. The rotor according to claim 5, wherein the rotor further
comprises axially directed fastening rails located on the surface
of the body part and attached to the body part, the bottom sections
of the permanent magnet modules are shaped to enable the permanent
magnet modules to be shape-locked in radial and circumferential
directions to the axially directed fastening rails and to enable
the permanent magnet modules to be slid in an axial direction along
the axially directed fastening rails, and the axially directed
fastening rails are arranged to press the permanent magnet modules
against the body part.
7. The rotor according to claim 6, wherein each of the axially
directed fastening rails has a T-shaped cross-section so that the
leg of the T-shaped cross-section is perpendicular to the surface
of the body part.
8. The rotor according to claim 6, wherein the rotor comprises
threaded elements extending radially through the body part to the
axially directed fastening rails and arranged to pull the axially
directed fastening rails towards the body part to press the
permanent magnet modules against the body part.
9. The rotor according to claim 5, wherein the permanent magnet
elements are arranged into the rows extending in the axial
direction so that the rows of the permanent magnet elements are
skewed with respect to the axial direction.
10. The rotor according to claim 5, wherein the permanent magnet
elements are arranged into V-shaped rows extending in the axial
direction.
11. The rotor according to claim 5, wherein the permanent magnet
elements are arranged into zigzag-shaped rows extending in the
axial direction.
12. A permanent magnet electric machine comprising: a stator, and a
rotor rotatably supported with respect to the stator, the rotor
comprising a body part having a shaft and permanent magnet modules
on a surface of the body part, wherein each of the permanent magnet
modules comprises a base-plate and a permanent magnet element
attached to the base-plate, the base-plate comprises a bottom
section and an upper section between the bottom section and the
permanent magnet element, and the permanent magnet modules
constitute at least three subsets of the permanent magnet modules
so that the permanent magnet modules of different ones of the
subsets differ from each other by positions of the upper sections
of the base-plates with respect to the bottom sections of the
base-plates so that the permanent magnet elements of the permanent
magnet modules of the different ones of the subsets are axially
successive and circumferentially at different positions when the
bottom sections of these permanent magnet modules are axially
successive and circumferentially aligned with each other on the
surface of the body part, and wherein the permanent magnet elements
of the permanent magnet modules are arranged into rows extending in
an axial direction of the rotor and deviating from the axial
direction of the rotor, and the bottom sections of the permanent
magnet modules are arranged into axially directed straight
rows.
13. A method for assembling a permanent magnet electric machine,
the method comprising: installing a body part of a rotor of the
permanent magnet electric machine on an operational position where
a surface of the body part faces radially towards an airgap surface
of a stator of the permanent magnet electric machine, and
subsequently sliding, in an axial direction of the rotor and along
the surface of the body part, permanent magnet modules to
operational positions of the permanent magnet modules, and
attaching the permanent magnet modules to the body part, wherein
each of the permanent magnet modules comprises a base-plate and a
permanent magnet element attached to the base-plate, the base-plate
comprises a bottom section and an upper section between the bottom
section and the permanent magnet element, and the permanent magnet
modules constitute at least three subsets of the permanent magnet
modules so that the permanent magnet modules of different ones of
the subsets differ from each other by positions of the upper
sections of the base-plates with respect to the bottom sections of
the base-plates so that the permanent magnet elements of the
permanent magnet modules of the different ones of the subsets are
axially successive and circumferentially at different positions
when the bottom sections of these permanent magnet modules are
axially successive and circumferentially aligned with each other on
the surface of the body part, and wherein the method comprises
arranging the permanent magnet elements of the permanent magnet
modules into rows extending in an axial direction of the rotor and
deviating from the axial direction of the rotor, and arranging the
bottom sections of the permanent magnet modules into axially
directed straight rows.
14. The method according to claim 13, wherein the rotor comprises
axially directed fastening rails located on the surface of the body
part and attached to the body part, the bottom sections of the
permanent magnet modules are shaped to enable the permanent magnet
modules to be shape-locked in radial and circumferential directions
to the axially directed fastening rails and to enable the permanent
magnet modules to be slid in an axial direction along the axially
directed fastening rails, and the method comprises sliding the
permanent magnet modules along the axially directed fastening rails
and attaching the permanent magnet modules to the body part by
pulling the axially directed fastening rails towards the body part.
Description
FIELD OF THE DISCLOSURE
The disclosure relates generally to a permanent magnet electric
machine that can be, for example but not necessarily, a generator
of a wind power plant. More particularly, the disclosure relates to
permanent magnet modules for a rotor of a permanent magnet electric
machine. Furthermore, the disclosure relates to a rotor of a
permanent magnet electric machine. Furthermore, the disclosure
relates to a permanent magnet electric machine. Furthermore, the
disclosure relates to a method for assembling a permanent magnet
electric machine.
BACKGROUND
An inherent advantage of a permanent magnet electric machine is a
good efficiency because permanent magnets generate magnetic field
without losses in contrast to electromagnets. On the other hand,
permanent magnet electric machines are not free from challenges.
One of the challenges is related to magnetic forces which are
generated by permanent magnets and which complicate installation of
a rotor of a permanent magnet electric machine. In conjunction with
large permanent magnet electric machines where the magnetic forces
are strong, a rotor is often installed without permanent magnets. A
body part of the rotor may comprise for example axially directed
fastening rails with the aid of which permanent magnet modules can
be slid in the axial direction into their final positions on a
surface of the body part after the body part has been arranged to
be supported by bearings with respect to a stator. The axially
directed fastening rails may have for example a T-shaped
cross-section so that the leg of the T-shaped cross-section is
perpendicular to the surface of the body part, and the permanent
magnet modules may have portions that are pressed by the axially
directed fastening rails against the body part when the axially
directed fastening rails are tightened towards the body part. The
rotor may comprise for example bolts or threaded rods extending
radially through the body part to the axially directed fastening
rails and suitable for pulling the axially directed fastening rails
towards the body part.
The above-described method for assembling a rotor of a permanent
magnet electric machine is not free from challenges. One of the
challenges is that the above-described method leads inherently to a
construction where permanent magnet modules are arranged in axially
directed straight rows on a surface of a body part of a rotor. For
example, to reduce cogging torque and/or voltage harmonics, there
can be a need to deviate from the above-mentioned construction
where the permanent magnet modules are arranged in the axially
directed straight rows. Instead, there can be a need to arrange the
permanent magnet modules into rows that are skewed with respect to
the axial direction or into rows that otherwise deviate from
axially directed straight rows.
SUMMARY
The following presents a simplified summary to provide a basic
understanding of some aspects of various invention embodiments. The
summary is not an extensive overview of the invention. It is
neither intended to identify key or critical elements of the
invention nor to delineate the scope of the invention. The
following summary merely presents some concepts of the invention in
a simplified form as a prelude to a more detailed description of
exemplifying and non-limiting embodiments.
In accordance with the invention, there are provided new permanent
magnet modules for a rotor of a permanent magnet electric machine.
The permanent magnet electric machine can be, for example but not
necessarily, a direct driven wind generator.
Each of the above-mentioned permanent magnet modules comprises a
base-plate and a permanent magnet element attached to the
base-plate. The base-plate comprises a bottom section and an upper
section between the bottom section and the permanent magnet
element. The permanent magnet modules constitute at least three
subsets of the permanent magnet modules so that the permanent
magnet modules of different ones of the subsets differ from each
other by positions of the upper sections of the base-plates with
respect to the bottom sections of the base-plates so that the
permanent magnet elements of the permanent magnet modules of
different ones of the subsets are axially successive and
circumferentially at different positions when the bottom sections
of these permanent magnet modules are axially successive and
circumferentially aligned with each other on a surface of a body
part of a rotor.
The above-described permanent magnet modules make it possible to
construct a rotor where the above-mentioned permanent magnet
elements and the upper sections of the base-plates are arranged
into a pattern that deviates from axially directed straight rows,
but where the bottom sections of the base-plates are arranged into
axially directed straight rows. For example, the permanent magnet
elements and the upper sections of the base-plates can be arranged
into rows skewed with respect to the axial direction while the
bottom sections of the base-plates are arranged into axially
directed straight, i.e. non-skewed, rows. As the bottom sections of
the base-plates that are attached to the body part are arranged
into axially directed straight rows, neither the assembly of the
rotor nor the fastening of the permanent magnet modules is
complicated.
In accordance with the invention, there is provided also a new
rotor for a permanent magnet electric machine. A rotor according to
the invention comprises: a body part having a shaft, and permanent
magnet modules according to the invention on a surface of the body
part.
In the rotor according to the invention, the permanent magnet
elements of the permanent magnet modules are arranged into rows
extending in the axial direction of the rotor and deviating from
the axial direction of the rotor, and the bottom sections of the
permanent magnet modules are arranged into axially directed
straight rows.
In accordance with the invention, there is provided also a new
permanent magnet electric machine that comprises a rotor according
to the invention and a stator, wherein the rotor is rotatably
supported with respect to the stator.
In accordance with the invention, there is provided also a new
method for assembling a permanent magnet electric machine. The
method comprises: installing a body part of a rotor of the
permanent magnet electric machine on an operational position where
a surface of the body part faces radially towards an airgap surface
of a stator of the permanent magnet electric machine, and
subsequently sliding, in an axial direction of the rotor and along
the surface of the body part, permanent magnet modules according to
the invention to operational positions of the permanent magnet
modules so that the permanent magnet elements of the permanent
magnet modules are arranged into rows extending in the axial
direction of the rotor and deviating from the axial direction of
the rotor, and the bottom sections of the permanent magnet modules
are arranged into axially directed straight rows, and attaching the
permanent magnet modules to the body part.
Exemplifying and non-limiting embodiments are described in
accompanied dependent claims.
Various exemplifying and non-limiting embodiments both as to
constructions and to methods of operation, together with additional
objects and advantages thereof, will be best understood from the
following description of specific exemplifying and non-limiting
embodiments when read in connection with the accompanying
drawings.
The verbs "to comprise" and "to include" are used in this document
as open limitations that neither exclude nor require the existence
of also un-recited features. The features recited in the
accompanied dependent claims are mutually freely combinable unless
otherwise explicitly stated. Furthermore, it is to be understood
that the use of "a" or "an", i.e. a singular form, throughout this
document does not exclude a plurality.
BRIEF DESCRIPTION OF FIGURES
Exemplifying and non-limiting embodiments and their advantages are
explained in greater detail below with reference to the
accompanying drawings, in which:
FIGS. 1a-1f illustrate a permanent magnet electric machine
according to an exemplifying and non-limiting embodiment,
FIGS. 2a and 2b illustrate rotors according to exemplifying and
non-limiting embodiments,
FIG. 3 illustrates permanent magnet modules according to an
exemplifying and non-limiting embodiment, and
FIG. 4 shows a flowchart of a method according to an exemplifying
and non-limiting embodiment for assembling a permanent magnet
electric machine.
DESCRIPTION OF EXEMPLIFYING AND NON-LIMITING EMBODIMENTS
The specific examples provided in the description below should not
be construed as limiting the scope and/or the applicability of the
accompanied claims. Lists and groups of examples provided in the
description are not exhaustive unless otherwise explicitly
stated.
FIG. 1a shows a section view of a part of a permanent magnet
electric machine according to an exemplifying and non-limiting
embodiment. The section is taken along a line A1-A1 shown in FIG.
1b and the section plane is parallel with the xy-plane of a
coordinate system 199. FIG. 1b shows a part of a rotor 118 of the
permanent magnet electric machine when seen along a radial
direction towards an airgap surface of the rotor. FIG. 1c shows
schematically the permanent magnet electric machine so that a
stator 121 of the permanent magnet electric machine is presented as
a section view, but the rotor 118 is not presented as a section
view. FIG. 1d shows a view of a section taken along a line A2-A2
shown in FIG. 1b, and FIG. 1e shows a view of a section taken along
a line A3-A3 shown in FIG. 1b. The section planes related to FIGS.
1d and 1e are parallel with the xy-plane of the coordinate system
199.
The rotor 118 is rotatably supported with respect to the stator 121
with a bearing system that is not shown in FIGS. 1a-1e. The rotor
118 comprises a body part 119 that comprises a shaft. The rotor 118
comprises permanent magnet modules mounted on a surface of the body
part 119. In FIGS. 1a, 1b, 1d, and 1e, some of the permanent magnet
modules are denoted with references 101, 102, 103, 104, 105, 106,
107, 108, and 109. The permanent magnet modules 102 and 105 are
shown in FIG. 1f.
Each of the permanent magnet modules comprises a base-plate and a
permanent magnet element attached to the base-plate. In FIG. 1f,
the base-plates of the permanent magnet modules 102 and 105 are
denoted with a reference 110 and the permanent magnet elements of
the permanent magnet modules 102 and 105 are denoted with a
reference 111. The direction of magnetization of the permanent
magnet elements 111 is parallel with the y-axis of the coordinate
system 199. Thus, the permanent magnet elements of the permanent
magnet modules shown in FIGS. 1a, 1b, 1d, and 1e have radial
directions of magnetization. Each permanent magnet element can be
for example a single piece of permanent magnet material that is
attached, e.g. with glue, on a surface of the base-plate. It is
also possible that a permanent magnet element comprises a casing
inside which there are one or more pieces of permanent magnet
material. It is worth noting that permanent magnet elements of
various kinds are possible in conjunction with the permanent magnet
modules under consideration.
The base-plate of each permanent magnet module comprises a bottom
section and an upper section between the bottom section and the
permanent magnet element of the permanent magnet module. In FIG.
1f, the bottom sections of the permanent magnet modules 102 and 105
are denoted with a reference 112 and the upper sections of the
permanent magnet modules 102 and 105 are denoted with a reference
113. The permanent magnet modules constitute subsets of permanent
magnet modules so that permanent magnet modules of different ones
of the subsets differ from each other by positions of the upper
sections of the base-plates with respect to the bottom sections of
the base-plates. In the exemplifying permanent magnet electric
machine illustrated in FIGS. 1a-1e, the permanent magnet modules
101-103 belong to a first subset, the permanent magnet modules
104-105 belong to a second subset, and the permanent magnet modules
107-109 belong to a third subset. Thus, the permanent magnet
modules 102 and 105 shown in FIG. 1f belong to different subsets.
As shown in FIG. 1f, these permanent magnet modules 102 and 105
differ from each other by the positions of the upper sections 113
of the base-plates 110 with respect to the bottom sections 112 of
the base-plates 110. Each base-plate can be for example a single
piece of steel or other suitable material. It is however also
possible that a base-plate is composed of e.g. two pieces of steel
or other suitable material.
In the exemplifying permanent magnet electric machine illustrated
in FIGS. 1a-1e, the rotor 118 comprises axially directed fastening
rails located on the surface of the body part 119. The axial
direction is parallel with the z-axis of the coordinate system 199.
In FIG. 1a, one of the axially directed fastening rails is denoted
with a reference 129. In this exemplifying case, each of the
axially directed fastening rails has a T-shaped cross-section so
that the leg of the T-shaped cross-section is perpendicular to the
surface of the body part 119. The rotor 118 comprises threaded
elements extending radially through the body part 119 to the
axially directed fastening rails. In FIG. 1a, one of the threaded
elements is denoted with a reference 120. In this case, the
threaded elements are bolts but as well they could be threaded rods
with nuts. The threaded elements are suitable for pulling the
axially directed fastening rails towards the body part 119. The
bottom sections of the permanent magnet modules are shaped so that
the permanent magnet modules are shape-locked in radial and
circumferential directions by the axially directed fastening rails.
In FIGS. 1a and 1b, the circumferential direction is depicted with
an arrow .phi.. When the threaded elements are loose i.e. not
tightened, the permanent magnet modules can be slid in the axial
direction along the axially directed fastening rails. Thus, the
permanent magnet modules can be installed by sliding the permanent
magnet modules axially along the axially directed fastening rails
on the surface of the body part 119 after the body part 119 has
been installed on its operational position with respect to the
stator 121. Thereafter, the permanent magnet modules can be
attached to the body part 119 by tightening the threaded elements
resulting in a situation in which the axially directed fastening
rails press the permanent magnet modules against the body part
119.
As shown in the section views shown in FIGS. 1a, 1d, and 1e, the
bottom sections of the permanent magnet modules 101, 104, and 107
are aligned with each other in the circumferential direction.
Correspondingly, the bottom sections of the permanent magnet
modules 102, 105, and 108 are aligned with each other in the
circumferential direction, and the bottom sections of the permanent
magnet modules 103, 106, and 109 are aligned with each other in the
circumferential direction. As the permanent magnet modules 101-103
differ from the permanent magnet modules 104-105 by the positions
of the upper sections of the base-plates with respect to the bottom
sections of the base-plates and correspondingly the permanent
magnet modules 104-106 differ from the permanent magnet modules
107-109 in the above-mentioned way, the permanent magnet elements
of the permanent magnet modules are not arranged into axially
directed straight rows. In this exemplifying case, the permanent
magnet elements of the permanent magnet modules are arranged into
rows extending in the axial direction so that the rows are skewed
with respect to the axial direction by a skewing angle .alpha. that
is shown in FIG. 1b.
FIG. 2a illustrates a part of a rotor according to an exemplifying
and non-limiting embodiment. The viewing direction related to FIG.
2a corresponds to the viewing direction related to FIG. 1b. Two of
the permanent magnet modules are denoted with references 201 and
202. In this exemplifying case, the permanent magnet elements of
the permanent magnet modules are arranged into V-shaped rows
extending in the axial direction. The axial direction is parallel
with the z-axis of a coordinate system 299. The V-shape is
illustrated with a dashed polyline 261. FIG. 2b illustrates a part
of a rotor according to another exemplifying and non-limiting
embodiment. The viewing direction related to FIG. 2b corresponds to
the viewing direction related to FIG. 1b. Two of the permanent
magnet modules are denoted with references 203 and 204. In this
exemplifying case, the permanent magnet elements of the permanent
magnet modules are arranged into zigzag-shaped rows extending in
the axial direction. The axial direction is parallel with the
z-axis of a coordinate system 299. The zigzag-shape is illustrated
with a dashed polyline 262.
In the exemplifying permanent magnet modules illustrated in FIGS.
1a, 1b, 1d, 1e, and 1f, the bottom section of each permanent magnet
module comprises fastening edges for shape-locking the permanent
magnet module under consideration in the radial and circumferential
directions to between adjacent ones of the axially directed
fastening rails as illustrated in FIGS. 1a, 1d, and 1e. In FIG. 1f,
the fastening edges of the permanent magnet modules 102 and 105 are
denoted with references 114 and 115. The fastening edge 114
comprises a flange section 116 and the fastening edge 115 comprises
a flange section 117. The flange sections enable the axially
directed fastening rails to press the permanent magnet module under
consideration against the body part 119 of the rotor 118 as
illustrated in FIGS. 1a, 1d, and 1e.
The exemplifying permanent magnet electric machine illustrated in
FIGS. 1a-1e, is an inner rotor electric machine. The
above-described principles for constructing a rotor of a permanent
magnet electric machine are applicable on outer rotor electric
machines, too. As shown in FIGS. 1a, 1d, and 1e, the permanent
magnet modules are attached on the convex surface of the body part
119. In an outer rotor electric machine according to an
exemplifying and non-limiting embodiment, permanent magnet modules
according to an embodiment of the invention are attached on the
concave surface of a body part of a rotor.
FIG. 3 shows permanent magnet modules 302 and 303 according to an
exemplifying and non-limiting embodiment. Each of the permanent
magnet modules comprises a base-plate 310 and a permanent magnet
element 311 attached to the base-plate. The base-plate comprises a
bottom section 312 and an upper section 313 between the bottom
section 312 and the permanent magnet element 311. The permanent
magnet modules 302 and 303 differ from each other by the positions
of the upper sections of the base-plates with respect to the bottom
sections of the base-plates so that the permanent magnet elements
of the permanent magnet modules are successive in the z-direction
of a coordinate system 399 and at different positions in the
x-direction of the coordinate system 399 when the bottom sections
of the permanent magnet modules 302 and 305 are successive in the
z-direction of the coordinate system 399 and aligned with each
other in the x-direction of the coordinate system 399. In this
exemplifying case, the bottom section 312 of each of the permanent
magnet modules has a dovetail-shaped groove 322 so that the
permanent magnet modules can be slid along fastening rails having a
dovetail shaped cross-section. The permanent magnet modules can be
attached to a body part of a rotor with means, e.g. bolts, for
pulling the fastening rails towards the body part.
In the above-described exemplifying cases, the permanent magnet
modules are slid along axially directed fastening rails that are
used also for attaching the permanent magnet modules to the body
part of the rotor. It is however also possible to use a temporarily
mounted and removable installation device for axially sliding
permanent magnet modules one-by-one into their final positions on a
surface of a body part of a rotor, and thereafter to fasten each
permanent magnet module to the body part with e.g. one or more
bolts extending radially through the body part to the permanent
magnet module under consideration. The principle that the bottom
portions of the permanent magnet modules form axially directed
straight rows even if the permanent magnet elements form rows
deviating from the axial direction, can be helpful also in the
cases where there are no axially directed fastening rails.
FIG. 4 shows a flowchart of a method according to an exemplifying
and non-limiting embodiment for assembling a permanent magnet
electric machine. The method comprises the following actions:
action 401: installing a body part of a rotor of the permanent
magnet electric machine on an operational position where a surface
of the body part faces radially towards an airgap surface of a
stator of the permanent magnet electric machine, and subsequently
action 402: sliding, in an axial direction of the rotor and along
the surface of the body part, permanent magnet modules according to
an embodiment of the invention to operational positions of the
permanent magnet modules so that the permanent magnet elements of
the permanent magnet modules are arranged into rows extending in
the axial direction of the rotor and deviating from the axial
direction of the rotor, and the bottom sections of the permanent
magnet modules are arranged into axially directed straight rows,
and action 403: attaching the permanent magnet modules to the body
part.
In a method according to an exemplifying and non-limiting
embodiment, the rotor comprises axially directed fastening rails
located on the surface of the body part and attached to the body
part. In this exemplifying case, the permanent magnet modules are
slid along the axially directed fastening rails and attached to the
body part by pulling the axially directed fastening rails towards
the body part.
In a method according to an exemplifying and non-limiting
embodiment, each of the axially directed fastening rails has a
T-shaped cross-section so that the leg of the T-shaped
cross-section is perpendicular to the surface of the body part.
In a method according to an exemplifying and non-limiting
embodiment, the permanent magnet modules are attached to the body
part by tightening threaded elements, e.g. bolts, extending
radially through the body part to the axially directed fastening
rails to make the axially directed fastening rails to press the
permanent magnet modules against the body part.
In a method according to an exemplifying and non-limiting
embodiment, the permanent magnet elements of the permanent magnet
modules are arranged into the rows extending in the axial direction
so that the rows are skewed with respect to the axial
direction.
In a method according to an exemplifying and non-limiting
embodiment, the permanent magnet elements are arranged into
V-shaped rows extending in the axial direction.
In a method according to an exemplifying and non-limiting
embodiment, the permanent magnet elements are arranged into
zigzag-shaped rows extending in the axial direction.
The specific examples provided in the description given above
should not be construed as limiting the scope and/or the
applicability of the appended claims. Lists and groups of examples
provided in the description given above are not exhaustive unless
otherwise explicitly stated.
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